Lives could be in danger because road signs are increasingly obscured by overgrown vegetation by the side of the carriageway.

Lives could be in danger because road signs are increasingly obscured by overgrown vegetation by the side of the carriageway, the AA has warned.

The situation could enable speeding motorists to escape being fined if they claimed they did not see a sign with the limit on, the motoring organisation said.

The problem was worse than ever this year because of ideal growing conditions.

The warning came as Government figures showed that two in every three cars break the speed limit in urban areas.

Paul Watters, the AA's head of roads and transport policy, said, "The situation is nothing short of ridiculous. It is even getting to the stage where the police may not be able to enforce speeding offences if speed limit signs are covered.

"Signs are essential for road safety, but if they can't be read they may as well not be there in the first place."

He also encouraged motorists to consider claiming against the highway authority if they had an accident or committed a motoring offence because they were unable to read a sign.

A code of practice for highway maintenance was recently published and should lead to roadside vegetation being cut back more frequently.

The AA said it would monitor the situation closely to ensure councils stuck to it. Highway authorities have a legal duty to keep road signs visible at all times, and this new code will inevitably be tested in court, a spokeswoman predicted.

The AA urged drivers to report any obscured signs they came across to the local council.

A spokesman for the Department for Transport, Local Government and the Regions agreed that councils should keep signs clear in case they led to drivers inadvertently breaking the law.

But he added, "Drivers should know what the limits are. If they are driving in a built-up area, the limit is almost always 30mph. On a motor-way, it is 70mph and on open, single-carriage roads, it is 60mph.

"I wouldn't have thought speeding motorists would have much success against the police because there are plenty of other factors they should be taking into account when considering how fast to drive."